Elizabeth(pseudonym) has been stressed from relationships between her co-workers lately. She often feels heat flaring up to her face and palpitation during meetings, which makes her hard to converse normally. Even after she comes home, it is hard for her to calm down and it takes her 1-2 hours before she falls asleep. She also experiences frequent heartburn and occasional abdominal pain.
Elizabeth is currently showing typical symptoms of SNS (sympathetic nervous system) hyperactivity. SNS comes into action when we have the flight-or-flight response (aka acute stress response.) For example, we confront a bear in the woods. To fight or flight, we require a large amount of blood supply to the muscle tissues, and our heart rate goes up to pump more blood. Thus the patient experiences palpitation. Increased blood flow to the muscle tissues naturally reduces blood supply to the gastrointestinal system, because digesting food matters very little when we are in life or death situation. Thus, digestive issues arise such as loss of appetite, heartburn, bloating and acid reflux altogether with sleep problem from being very alert to changes (confronting stress or a bear) to her surroundings.
Certainly, not everyone rapidly reacts to stress like Elizabeth. We know that there is always one friend who can sleep through a fire alarm no problem. Thus, those who are hot-tempered, strongly opinionated easily develop symptoms like Elizabeth. Of course, patients who are introverted can also suffer from hyperactivity of SNS, but they will not show skin sensitivity or red face (heat flare up to the face.)